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  • Polymer and Materials Science  (7)
  • EARTH RESOURCES AND REMOTE SENSING  (6)
  • 1990-1994  (13)
  • 1
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Computational techniques have been used to aid interpretation of observed systematic shifts in the amide III frequencies of Ala-X peptides. Optimized structures and frequencies have been calculated for Ala-X peptides using GAUSSIAN86/88 with the 4-31G basis, MOPAC, and normal mode methods based on empirical force fields. We observe the following: (1) Frequencies calculated using scaled GAUSSIAN86 force constants correlate well with the experimental results. (2) Structures of the Ala-X peptides optimized by GAUSSIAN show a clear trend toward lower values of the dihedral angle φ as the X side chain becomes larger, while structures optimized here using semiempirical and empirical force fields do not show trends. (3) Computational changes in peptide conformations from β-sheet to α-helix produce large changes in both amide I and amide III frequencies that are inconsistent with the experimental results. (4) Computational changes in the dihedral angle φ of Ala-Ala produce a change in the amide III frequency consistent with the experimental results. (5) The experimental frequency shifts cannot be attributed directly to the effects of changing mass.
    Additional Material: 7 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 33 (1993), S. 1519-1535 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A quantitative understanding of helix-coil dynamics will help explain their role in protein folding and in folded proteins. As a contribution to the understanding, the equilibrium and dynamical aspects of the helix-coil transition in polyvaline have been studied by computer simulation using a simplified model of the polypeptide chain. Each amino acid residue is treated as a single quasiparticle in an effective potential that approximates the potential of mean force in solution. The equilibrium properties examined include the helix-coil transition and its dependence on chain position and well depth at the coil-helix interface. A stochastic simulation of the Brownian motion of the chain in its solvent surroundings has been used to investigate dynamical properties. Time histories of the dihedral angles have been used to study the behavior of the helical structure. Auto and cross-correlation functions have been calculated from the time histories and from the state (helix or coil) functions of the residues with relaxation times of tens to hundreds of picoseconds. Helix-coil rate constants of tens of ns-1 were found for both directions of the transition. © 1993 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Raman spectra of series of aqueous solutions of peptides containing two amino acids, glycine-X, alanine-X, and serine-X, where X is an uncharged amino acid, show that the amide III band shifts systematically to lower frequencies as the side chain of the X amino acid becomes larger. The range of this shift is about 20cm-1, starting at 1275cm-1 for alanine-glycine and moving to 1251 cm-1 for alanine-tryptophan, with a correlation coefficient of 0.93 with the mass of the X amino acid side chain for 10 peptides. The amide I frequencies remain constant as the X amino acid is changed. This shift may result from a change in the average conformational preference of the peptide, a change in vibrational coupling of the amide III modes with the X amino acid side chain, a change in molecular force constants, or a combination of these. These results present a test for computational methods.
    Additional Material: 3 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 32 (1992), S. 477-490 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interhelical interfaces have been examined in seven high-resolution globin chains. The profiles of hydrophobic contact, as measured by the residue solvent-accessible area loss upon folding, have been calculated. The seven globins studied differ in their overall loss of solvent-accessible area upon packing of their helices, the order being 1MBD 〉 1LH1 〉 1ECD 〉 2MHBB 〉 2HHBB 〉 2HHBA 〉 2MHBA, which gives a measure of the difference in stability due to the hydrophobic interaction. The five helix-pair packings (AH, BE, BG, FH and GH) examined in detail have qualitative similarities. There are, however, substantial quantitative differences both at the equivalent residue level and at the level of overall helix-helix contact, which has significance in some models of folding. The AH pair has the most uniform area loss over the seven globins and the largest variation in accessible area loss on packing among the five helix pairs is the GH pair. The set of residues required to produce the globin fold has been deduced from the residue area losses.
    Additional Material: 2 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 2263-2270 
    ISSN: 0887-6266
    Keywords: PDAMC ; cyclopolymerization ; cyclopolymer ; poly(diallydimethylammonium chloride) ; CPMAS ; nitrogen-14 ; nitrogen-15 ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: CPMAS 13C and 15N solid-state NMR spectroscopy, as well as solution state 14N NMR spectroscopy, was used to investigate the microstructure of poly (diallyldimethylammonium chloride). The results of these studies, supported by 14N NMR studies of model compounds, were in agreement with the earlier conclusion of other workers (via solution state 13C NMR spectroscopy) that the polymer consists of a chain of five-membered pyrrolidinium rings, A. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 48 (1993), S. 1701-1707 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Solid-state NMR and thermal analysis techniques were used to compare the mobility of poly(vinyl butyral) (PVB) in the presence and absence of both alumina filler particles and plasticizer. The relative mobility of main-chain and side-chain carbons increases in the presence of both plasticizer and alumina as seen from an increase in the average cross-polarization rates, 〈TCH〉, and from a general decrease in the rotating frame spin-lattice relaxation rates, CT1ρ. Unlike the main-chain carbons, inversion recovery cross-polarization (IRCP) data on solution cast composites show that the side-chain methyl groups in neat PVB samples are best characterized by a monoexponential cross-polarization model. However, in the presence of alumina, a fraction of the methyl groups becomes less mobile as indicated by the biexponential IRCP behavior. Polymer phase mobility also increases below the critical pigment volume concentration (CPVC) as seen from decreasing transition temperatures using dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). This is accompanied by an increase in the rigidity of a portion of the polymer phase above the CPVC as indicated by an increase in the apparent Tg, along with an increase in the mobility of another portion as indicated by the appearance of a low-temperature DMA transition. These trends are consistent with an increase in polymer chain packing heterogeneity in the presence of alumina. © 1993 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 15 (1990), S. 451-453 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Samples suitable for sputter depth profiling of surface films from the substrate into the film have been produced by selective removal of most of the underlying silicon substrate. This procedure, which reduces problems due to collisional mixing and redeposition of sputtered material, was accomplished by the controlled growth of a boron-rich etch-stop layer using molecular beam epitaxy followed by selective chemical etching. The usefulness of this approach has been demonstrated by studying the redistribution of As during the growth of platinum and cobalt silicides with secondary ion mass spectrometry (SIMS).
    Additional Material: 2 Ill.
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  • 8
    Publication Date: 2013-08-31
    Description: Broadband scanning radiometers have been used extensively on earth-orbiting satellites to measure the Earth's outgoing radiation. The resulting estimates of longwave and shortwave fluxes have played an important role in helping to understand the Earth's radiant energy balance or budget. The Clouds and the Earth Radiant Energy System (CERES) experiment is expected to include instruments with three broadband scanning radiometers. The design of the CERES instrument will draw heavily from the flight-proven Earth Radiation Budget Experiment (ERBE) scanner instrument technology and will benefit from the several years of ERBE experience in mission operations and data processing. The discussion starts with a description of the scientific objectives of ERBE and CERES. The design and operational characteristics of the ERBE and CERES instrument are compared and the two ground-based data processing systems are compared. Finally, aspects of the CERES data processing which might be performed in near real-time aboard a spacecraft platform are discussed, and the types of algorithms and input data requirements for the onboard processing system are identified.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Earth Sciences Requirements for the Information Sciences Experiment System; p 91-103
    Format: application/pdf
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  • 9
    Publication Date: 2019-06-28
    Description: Instruments of the Earth Radiation Budget Experiment (ERBE) are operating on three different Earth orbiting spacecrafts: the Earth Radiation Budget Satellite (ERBS), NOAA-9, and NOAA-10. An overview is presented of the ERBE mission, in-orbit environments, and instrument design and operational features. An overview of science data processing and validation procedures is also presented. In-flight operations are described for the ERBE instruments aboard the ERBS and NOAA-9. Calibration and other operational procedures are described, and operational and instrument housekeeping data are presented and discussed.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA-RP-1256 , L-16895 , NAS 1.61:1256
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  • 10
    Publication Date: 2019-06-28
    Description: In the past six months, work has continued on energy flux sensitivity studies, ice surface temperature retrievals, corrections to Advanced Very High Resolution Radiometer (AVHRR) thermal infrared data, modelling of cloud fraction retrievals, and radiation climatologies. We tentatively conclude that the SSM/I may not provide accurate enough estimates of ice concentration and type to improve our shorter term energy flux estimates. SSM/I derived parameters may still be applicable in longer term climatological flux characterizations. We hold promise for a system coupling observation to a ice deformation model. Such a model may provide information on ice distribution which can be used in energy flux calculations. Considerable variation was found in modelled energy flux estimates when bulk transfer coefficients are modulated by lead fetch. It is still unclear what the optimum formulation is and this will be the subject of further work. Data sets for ice surface temperature retrievals were assembled and preliminary data analysis was started. Finally, construction of a conceptual framework for further modelling of the Arctic radiation flux climatology was started.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA-CR-192129 , NAS 1.26:192129
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